Well , depending on the caliper you've got , you'd have to buy a disc that's the right diameter to suit the caliper and also fits the bolt spacings in the hub ... Most likely a 210 mm disc ... Since it's probably different to a chinese disc ... your wallet will be thinned out a lot more than $20 + postage for one ...
For the left side spacer you could get away with modifying a standard spacer off a bike with a 15 mm axle ...
You'd have to weigh up the costs of buying a complete chinese front wheel and disc or going with the Sano hub ... The Sano hub will be much stronger if you use Buchanan staino spokes and an Excell or whatever rim ... but IF you clench and fart just thinking about the cost... you're going to sh*t yourself when you find out the true the price ...
